“Some sharks, like great whites, must keep swimming to push water over their gills, but others, like nurse sharks, can rest on the seafloor and pump water over their gills instead.”

Reference: Smithsonian Ocean

More animal facts

The harmless whale shark holds the title of largest fish, with the record being a 59 footer captured in Thailand in 1919.

Sharks apparently are the only animals that never get sick. As far as is known, they are immune to every known disease including cancer.

The Labrador Retriever has a thick, rounded, tapering "otter tail" that works like a rudder, helping the dog steer while it swims.